Percutaneous access devices (PADs) are artificially created apertures in the skin that establish a permanent passageway between the inside and the outside of the body without interfering with host homeostasis. PADs have multiple potential uses and have been studied extensively in relation to permanently implanted prostheses that augment the action of the failing heart. Present cardiac assist systems depend on electrical or pneumatic power, which must be transmitted across or through the skin. As yet, however, a PAD that is reliable in long-term use has not been developed. To prevent infection, the major cause of PAD failure, and to assure trouble-free operation, we postulate the PAD design must provide for (1) control of epidermal proliferation and migration in proximity to the implant, and (2) attenuation of local strain. A PAD hypothesized to meet these requirements is being studied in rats and swine. Its neck (the transcutaneous portion) is nanoporous; a Dacron velour-covered flange joined to the neck is placed subdermally. Prior to implantation, autologous fibroblasts are cultured onto the PAD neck, forming a multilayer coating. The results to date indicate that PADs prepared in this way inhibit epithelial down-growth, whereas uncoated implants fail as a result of epidermal migration and infection. The objective of this Phase I project is to transfer and extend in sheep (which increasingly are used for full-scale testing of cardiac assist systems) the methodology evolved in swine. Specific aims are: (1) to adapt techniques for in vitro fibroblast proliferation and collagen production on the PAD neck to sheep cells; (2) to adapt surgical techniques for PAD implantation to sheep; and (3) to develop a protocol for long-term evaluation in sheep of a functioning PAD transferring power to an implanted heart assist device. The long-range goal is to qualify a PAD and make it commercially available for clinical use in conjunction with a system for treatment of patients in severe, chronic left heart failure. In addition, availability of the PAD for sheep will facilitate its adoption for preclinical evaluation of various mechanical heart assist system by others. This program will also lead to improved PADs for other commercial applications such as vascular access for kidney dialysis and skeletal attachment of prosthetic limbs.